The present invention generally involves connectors for piping and more particularly discloses what is generally termed a "quick connector" or union. This invention, in one particular embodiment, is useful in the drilling, production, and workover of oil and gas wells.
In large industrial operations and more particularly in the oil and gas industry it is often desirable and many times imperative that extremely high pressure fluids be pumped continuously from large powerful pumping systems into hydraulicly driven machinery or, as in the case of oil well servicing, directly into the borehole penetrating the underground formation. The fluids pumped encompass a broad range of liquids, some caustic and corrosive, some abrasive, and some very viscuous.
Oftentimes it is imperative to be able to place a movable pumping system, such as a truck or skid mounted hydraulic intensifier, at an oil well site and quickly supply high pressure fluid to the wellbore to acidize, fracture, or kill and prevent a blowout of the oilwell. The pumping system is usually connected to the wellbore by piping commonly called steel hose, and the connections between the sections of hose, the truck, and the wellhead must be capable of quick connections, good sealing ability, and high pressure capability under abrasive and corrosive conditions.
Conventional connectors for steel hose generally comprise a male connector end and a female connector end. The male end or the female end normally carries a primary seal consisting of a resilient seal such as an elastomeric radial seal or an O-ring seal. A secondary metal-to-metal seal may be attempted to back up the primary seal. One example of such a connector is disclosed in the '78-79 World Oil Catalog at page 2513 and is designated the Weco.sup.R Misaligning Union.
This conventional union has as its primary seal an elastomeric O-ring located in the male portion of the connector. Both the male and female connectors have arcuate seating shoulders to allow misalignment of the two pieces of up to 15.degree..
One of the major defects of the conventional connector assemblies is the use of an elastomeric seal as the primary seal. This exposes the seal to the high-pressure corrosive and abrasive environment passing through the piping. It also tends to extrude the seal into the flowstream which eventually results in the seal member blowing inward into the flowstream and lodging in a sensitive flow meter or other analytical instrument downstream from the connector. This is a particularly bad problem when the connectors are used in the production piping leading away from a high pressure oil or gas well.
Another serious defect of the conventional connectors is their tendency to vibrate loose or "back off" when in service. Because of the nature of these connectors and their use of an elastomeric primary seal, only a small amount of unthreading of the connector union allows loosening of the male and female ends to where the seal is quickly and easily pulled into the flowstream causing not only a loss of pressure at the connection, but also the accompanying damage to downstream instruments and tools. Because the conventional unions make-up and seal only at the very end of their confinement, a loosening of as little as one-fourth turn on the union by backing off of the thread can cause seal loss.
Backing off of the threaded portion of a connector can be a common occurrence due to several factors. One factor is the constant physical vibration from the pump motors to which the connection is attached. A second factor contributing to back-off is the constant high-pressure pump surges which cause the hydraulics to act internally and externally to loosen the connectors.
The present invention overcomes these deficiencies of the prior art by providing a quick connector which utilizes an interference-fit primary metal-to-metal seal backed up by a secondary elastomeric seal and having a locking means to prevent backing off of the threaded portions.